1. Technical Field
The present invention relates to semiconductor manufacturing equipment, and more particularly, to an air cleaning system for controlling impurity or pollution particles in the air within a clean room.
2. Description
Recently, research to prevent process defects in a semiconductor wafer manufacturing process, and to increase the production yield, is being actively pursued in conformity with the rapid development of semiconductor devices. It is being inevitably required to increase the degree to which air within a clean room is cleaned, which greatly influences an improvement in the production yield of the semiconductor devices. The clean room is provided as a space independent and isolated from a peripheral or surrounding environment, to produce a nearly-pollution-free environment by eliminating impurity or pollution particles typically existing in air.
FIG. 1 is a plan view schematically illustrating a conventional clean room, and the directions of the arrows indicate the air flow direction therein.
Referring to FIG. 1, a clean room 1 is isolated from the outside to independently control temperature and humidity therein. Clean air, having had undesirable impurity or pollution particles removed therefrom, circulates in the clean room 1. The clean room 1 is largely classified into a working area 5 and a service area 3.
The working area 5 is also called a bay, and a boat, having wafers mounted therein is disposed inside and is moved therein by a worker or robot. The service area 3 contains a unit process region where semiconductor equipment is positioned for performing various processes on the wafer after it is returned from the working area 5. The unit process region includes a wafer process area 7 performing some processes or operations on the wafer, and a wafer transfer area 9 for loading and unloading the wafer from the wafer process area 7.
The boat having the wafers mounted therein is moved from the working area 5 to the wafer transfer area 9 by a worker, and then a robot of the wafer transfer area 9 loads the wafers onto a wafer stage one by one and also unloads the process-completed wafers from the wafer process area 7.
The clean room 1 is designed so as not to cause an air inflow from the outside by maintaining the air pressure inside to be higher than the atmospheric pressure, and is controlled so that the air pressure of the working area 5 is higher than that of the service area 3. This pressure difference prevents microparticles generated in the service area 3 from flowing into the working area 5 provided as the wafer movement area. The pressure difference is obtained by controlling the amount of clean air flowing between the working area 5 and the service area 3.
FIG. 2 is an elevation view along line I˜I′ in FIG. 1. With reference to FIG. 2, in an upper part of the clean room 1 an upper plenum 11 is provided to supply primarily purified clean air, and in a lower part of the clean room 1 a lower plenum 13 opposite to the upper plenum 11 is formed to collect the air passed through the clean room 1.
The clean air supplied from the upper plenum 11 is passed through a first air filter 15, and is then passed through the working area 5 and the service area 3, and simultaneously the particles generated in the working area 5 and the service area 3 are discharged together with the clean air through the lower plenum 13 maintaining a low pressure. The working area 5 and the service area 3 are isolated vertically and independently from each other, by the first air filter 15 and a grating 17 that has air holes through which air is passed, the first air filter 15 being adapted to remove particles from air in the upper and lower plenums.
The volume of clean air flowing in the working area 5 and the service area 3 is controlled by the size of the first air filter 15 and the number of gratings 17, or the number of air holes, etc.
Though not shown in the drawing, the air collected from the lower plenum 13 is recirculated back to the upper plenum 11 by using a specific blast unit (e.g., a fan). At least one particle measurer is installed in the working area 5, and is managed to have and maintain in the working area 5 air that is cleaner and more purified than in the service area 3.
Also, air that is even cleaner and more purified than in the service area 3 and the working area 5 is supplied to the wafer process area 7 and the wafer transfer area 9 by using an air supply device 19 (see FIG. 3) for additionally (secondarily) purifying the clean air supplied from the service area 3 and the working area 5.
FIG. 3 illustrates in greater detail the wafer process area 7 and the wafer transfer area 9 shown in FIG. 2.
Referring to FIG. 3, the air supply device 19 includes a second air filter 19a and an air blast (e.g., fan) 19b, and sucks and purifies air of the working area 5 or the service area 3, then supplies it to the wafer process area 7 and the wafer transfer area 9. In some cases, air input to the air supply device 19 may be supplied from the lower plenum 13, and the air supply device 19 itself may be positioned within the lower plenum 13.
Furthermore, in the system of FIG. 3, an ion implantation device 21 is installed in the wafer process area 7, and a robot 27 is provided in the wafer transfer area 9. The robot 27 is adapted to remove a wafer from the boat 23 transferred from the working area 5, and to load the wafer into the wafer process area 7 through a wafer gate 25. The robot 27 not only loads the wafer from the boat 23 to the working area 5, but also unloads the completed wafer from the working area 5 and returns it to the boat 23 after completion of an ion implantation process of the ion implantation device 21.
The bottom of the wafer process area 7 and the wafer transfer area 9 is closed by a wall body so as not to directly discharge the clean air supplied from the air supply device 19 to the lower plenum 13. A plurality of pedestals 31 are installed within the lower plenum 13 for supporting the clean room 1 containing the wafer process area 7 and the wafer transfer area 9.
Thus, the wafer process area 7 and the wafer transfer area 9 maintain pressure relatively higher than the service area 3 and the working area 5, by the clean air supplied from the air supply device 19. Therefore, the clean air supplied to the wafer process area 7 and the wafer transfer area 9 flows dispersedly to the working area 5 and/or the service area 3.
That is, the air flow between the wafer transfer area 9 and the working area 5 can be performed through a gap of the boat gate 29 through which the boat 23, having the numerous wafers mounted therein, passes, or through a gap formed in the periphery of a door 32 that is installed in the wafer gate 25. Meanwhile, air flow between the wafer process area 7 and the service area 3 is performed through micro-apertures or openings formed in the wall body.
An air filter of the air supply device 19 for supplying the clean air to the wafer process area 7 and the service area 3 should be exchanged periodically after the lapse of a predetermined fixed time interval. Meanwhile, a worker should regularly measure the air impurity level, or degree of cleanliness, of the air in the wafer process area 7 and the wafer transfer 9, and should exchange the second air filter 19a of the air supply device 19 with a new one when the air impurity level exceeds a predetermined fixed threshold.
In the conventional air cleaning system for semiconductor manufacturing equipment, a worker regularly measures the particle pollution state of the wafer transfer area 9, and the second air filter 19a should be exchanged with a new one periodically after a lapse of a predetermined fixed time interval.
However, the conventional air cleaning system for semiconductor manufacturing equipment has the following disadvantages.
First, the conventional air cleaning system for semiconductor manufacturing equipment generates a defect in an ion implantation process if the wafer transfer area 9 is polluted with particles due to a pollution of the second air filter of the air supply device 19. This defect can be discovered in a product test procedure after the lapse of time or after the completion of the semiconductor manufacturing process. That is, there is a disadvantage that the yield of the ion implantation process declines.
Secondly, in order to sense abnormal metallic particles generated from a dynamic factor such as the robot 27 for loading or unloading a wafer on/from the wafer transfer area 9, in the conventional air cleaning system for semiconductor manufacturing equipment a maintenance worker must be continuously stationed to manage the clean room 1. Otherwise, the productivity may decrease due to an efficiency decrease of production in case the worker takes too long to eliminate contamination of the wafer transfer area 9 caused by the pollution particles.
Accordingly, it would be desirable to provide an air cleaning system for semiconductor manufacturing equipment which is capable of monitoring in real-time the generation of particle pollution in a wafer transfer area, and is capable of increasing the production yield by preventing the particle pollution.
According to one aspect of the present invention, a semiconductor manufacturing system comprises a working area; and a service area, the service area comprising: a wafer process area, in which a semiconductor manufacturing process is performed; a wafer transfer area spatially connected to the wafer process area, the wafer transfer area being adapted to transfer a wafer from the working area to the wafer process area; an air supply device for supplying clean air to the wafer transfer area and the wafer process area; and a particle measurer adapted to measure in a real time an impurity particle count of air in the wafer transfer area.
Herewith, the wafer process area executes a semiconductor manufacturing process in the service area. The wafer transfer area is spatially connected to the wafer process area, and transfers a wafer from the working area to the wafer process area. The air supply device supplies clean air to the wafer transfer area and the wafer process area. The particle measurer detects a defect of the air supply device, and continuously measures a degree of air cleanliness in the wafer transfer area so as to sense a particle pollution abnormally generated in the wafer transfer area.